Li/SOCl.sub.2 and Li/SO.sub.2 Cl.sub.2 batteries capable of operating under such conditions are known.
Li/SO.sub.2 Cl.sub.2 batteries suffer from a problem which does not occur in Li/SOCl.sub.2 batteries; namely a high degree of cathode polarization. In order to remedy this problem it is possible to use cathodes which contain platinum or cathodes of active carbon having a large surface area per unit volume. These solutions are expensive or difficult to implement in the form of a porous support.
The aim of the present invention is to solve the above problem while providing cathodes for Li/SO.sub.2 Cl.sub.2 batteries using a technology analogous to that used for Li/SOCl.sub.2 batteries.
An article by Murphy, Krehl and Liang which appeared in Proc. 16th Intersoc. Energy Conversion Engineering Conf. (The American Soc. of Mechanical Engineers NY 1981 page 97) studies the effects of adding a halogen to the electrolyte of a non-activatable Li/SO.sub.2 Cl.sub.2 battery, and concludes that it is advantageous to add chlorine to SO.sub.2 Cl.sub.2 while excluding the other halogens. According to this article, the addition of chlorine increases safety margins when using batteries at temperatures lying in the range -32.degree. C. to +150.degree. C.
In order to improve the discharging conditions of activatable Li/SO.sub.2 Cl.sub.2 batteries, the Applicant has discovered that there is no advantage in adding chlorine, but in contrast adding bromine to the electrolyte provides surprising improvements. This is because the bromine acts as a catalyst and not as a polarizer.